U.S. patent number 4,331,451 [Application Number 06/117,915] was granted by the patent office on 1982-05-25 for catalytic gasification.
This patent grant is currently assigned to Mitsui Toatsu Chemicals, Inc., Toyo Engineering Corporation. Invention is credited to Kazuyoshi Isogaya, Katsutoshi Kikuchi, Eiiti Sugiyama, Kenji Yoshida.
United States Patent |
4,331,451 |
Isogaya , et al. |
May 25, 1982 |
Catalytic gasification
Abstract
A process for catalytic gasification of heavy oil of a specific
gravity of higher than 0.7 with steam or steam/oxygen-containing
gas characterized in that the heavy oil is contacted with chromium
oxide catalyst or a catalyst comprising a mixture of chromium oxide
and one or more of alkaline earth metal oxides, aluminum oxide,
zirconium oxide, nickel oxide and cobalt oxide. More particularly,
the present invention relates to a process for catalytic
gasification of heavy oil of a specific gravity of higher than 0.7
characterized in that the heavy oil is contacted with a
gasification catalyst comprising calcium aluminate, an alkali
aluminate or tungsten-containing nickel and then the heavy oil is
further contacted with said chromium oxide catalyst or chromium
oxide-containing catalyst.
Inventors: |
Isogaya; Kazuyoshi (Yokohama,
JP), Sugiyama; Eiiti (Odawara, JP),
Yoshida; Kenji (Fujisawa, JP), Kikuchi;
Katsutoshi (Fujisawa, JP) |
Assignee: |
Mitsui Toatsu Chemicals, Inc.
(Tokyo, JP)
Toyo Engineering Corporation (Tokyo, JP)
|
Family
ID: |
22375497 |
Appl.
No.: |
06/117,915 |
Filed: |
February 4, 1980 |
Current U.S.
Class: |
48/214A; 252/373;
423/652; 423/654; 48/215 |
Current CPC
Class: |
C01B
3/384 (20130101); C01B 3/40 (20130101); C01B
2203/1052 (20130101) |
Current International
Class: |
C01B
3/40 (20060101); C01B 3/00 (20060101); C01B
3/38 (20060101); C01B 003/38 () |
Field of
Search: |
;48/214A,215 ;252/373
;423/652,654 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2902845 |
|
Aug 1979 |
|
DE |
|
848319 |
|
Sep 1960 |
|
GB |
|
Other References
"The Condensed Chemical Dictionary", by Hawley, 1974, pp. 410 &
496..
|
Primary Examiner: Bashore, Jr.; S. Leon
Assistant Examiner: Goldman; Michael L.
Attorney, Agent or Firm: Blanchard, Flynn, Thiel, Boutell
& Tanis
Claims
What is claimed is:
1. A continuous catalytic gasification process for converting heavy
hydrocarbon distillate into a product gas which has a very low
methane content and high hydrogen and carbon monoxide contents,
which consists essentially of: feeding a mixture of ( 1) heavy
hydrocarbon distillate having a specific gravity of higher than 0.7
and (2) steam or a mixture of steam and oxygen-containing gas,
wherein the ratio of the number of moles of steam to the number of
carbon atoms in said hydrocarbon distillate is from 0.3 to 7, into
a reaction zone which is at a pressure of from atmospheric pressure
to 100 Kg/cm.sup.2 ; in said reaction zone, first flowing said
mixture through a space free of catalyst so that said mixture
remains in said space for from 0.05 to 5 seconds and the
temperature of said mixture leaving said space is higher than
500.degree. C., then flowing said mixture through a catalyst bed
consisting essentially of from 50 to 100 wt. % of chromium oxide
and the balance is one or more materials selected from the group
consisting of aluminum oxide, zirconium oxide, alkaline earth metal
oxides, nickel oxide and cobalt oxide, so that said mixture
contacts said catalyst bed for from 0.1 to 10 seconds and is
converted into said product gas and said product gas has a
temperature of from 800.degree. to 1100.degree. C. when it exits
from said catalyst bed, and then discharging said product gas from
the reaction zone.
2. A process as claimed in claim 1 in which said heavy hydrocarbon
distillate is atomized and said mixture is fed into said reaction
zone from a nozzle at a velocity of from 100 m/sec to sonic
velocity and at a temperature of higher than 300.degree. C.
3. A continuous catalytic gasification process for converting heavy
hydrocarbon distillate into a product gas which has a very low
methane content and high hydrogen and carbon monoxide contents,
which consists essentially of: feeding a mixture of (1) heavy
hydrocarbon distillate having a specific gravity of higher than 0.7
and (2) steam or a mixture of steam and oxygen-containing gas,
wherein the ratio of the number of moles of steam to the number of
carbon atoms in said hydrocarbon distillate is from 0.3 to 7, into
a reaction zone which is at a pressure of from atmospheric pressure
to 100 Kg/cm.sup.2 ; in said reaction zone, flowing said mixture
through a first catalyst bed consisting essentially of a first
catalyst selected from the group consisting of calcium aluminate,
alkali metal aluminate and tungsten-containing nickel catalyst,
said first catalyst being effective to convert the higher
hydrocarbons in said hydrocarbon distillate into lower
hydrocarbons, then flowing said mixture through a second catalyst
bed consisting essentially of from 50 to 100 wt. % of chromium
oxide and the balance is one or more materials selected from the
group consisting of aluminum oxide, zirconium oxide, alkaline earth
metal oxides, nickel oxide and cobalt oxide, so that said mixture
contacts said first and second catalyst beds for a total time of
from 0.1 to 10 seconds effective to complete the cracking and
gasification of the hydrocarbons and to form said product gas and
said product gas has a temperature of from 800.degree. to
1300.degree. C. when it exits from said second catalyst bed, and
then discharging said product gas from the reaction zone.
4. A method as claimed in claim 3 in which the volume of the second
catalyst bed is from 25 to 90 volume %, based on the total volume
of the first and second catalyst beds.
5. A continuous catalytic gasification process for converting
hydrocarbon distillation residue into a product gas which has a
very low methane content and high hydrogen and carbon monoxide
contents, which consists essentially of: feeding a mixture of (1)
atomized heavy hydrocarbon distillation residue having a specific
gravity of higher than 0.8 and (2) steam or a mixture of steam and
oxygen-containing gas, wherein the ratio of the number of moles of
steam to the number of carbon atoms in said hydrocarbon
distillation residue is from 0.3 to 7, into a reaction zone which
is at a pressure of from atmospheric pressure to 100 Kg/cm.sup.2 ;
in said reaction zone, flowing said mixture through a first
catalyst bed consisting essentially of a first catalyst selected
from the group consisting of calcium aluminate, alkali metal
aluminate and tungsten-containing nickel catalyst effective to
convert the higher hydrocarbons in said hydrocarbon distillation
residue into lower hydrocarbons, then flowing said mixture through
a second catalyst bed consisting essentially of from 50 to 100 wt.
% of chromium oxide and the balance is one or more materials
selected from the group consisting of aluminum oxide, zirconium
oxide, alkaline earth metal oxides, nickel oxide and cobalt oxide,
so that said mixture contacts said first and second catalyst beds
for a total time of from 0.1 to 10 seconds effective to complete
the cracking and gasification of the hydrocarbons and to form said
product gas and said product gas has a temperature of from
800.degree. to 1300.degree. C. when it exits from said second
catalyst bed, and then discharging said product gas from the
reaction zone.
6. A method as claimed in claim 5 in which the volume of the second
catalyst bed is from 25 to 90 volume %, based on the total volume
of the first and second catalyst beds.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for obtaining a gas of a
very low methane content but rich in hydrogen and carbon monoxide
by continuous catalytic gasification of heavy oil having a specific
gravity of higher than 0.7.
2. Description of Prior Art
As processes for the gasification of natural gas and light
hydrocarbons of petroleum fractions up to naphtha, there have been
known the partial oxidation process and the steam reforming process
wherein a nickel catalyst is used, and the partial oxidation
process wherein a catalyst is not used. On the other hand, for the
gasification of hydrocarbons containing heavy distillates such as
kerosene, gas oil and No. 2 fuel oil and heavy residues such as
crude oil, atmospheric residue and vacuum residue, only the
non-catalytic partial oxidation process is employed on an
industrial scale.
A gas obtained by the known process wherein heavy oils such as
heavy distillate and heavy residue are partially oxidized in the
absence of catalyst has a low methane content since the reaction
temperature in the partial oxidation is as high as
1300.degree.-1500.degree. C. and, therefore, it is used suitably as
an ammonia, methanol or oxo synthesis gas or as hydrogen gas for
hydrogenation. However, the non-catalytic partial oxidation process
has the following defects:
(1) Expensive oxygen or oxygen-rich air is required in a large
amount for maintaining a high reaction temperature.
(2) A great part of the raw oil is spent for the combustion for
obtaining a high temperature and, consequently, the yields of
H.sub.2 and CO are reduced.
(3) A reactor made of a heat-resistant material of a high grade is
required because of the high reaction temperature and the life of
the reactor is short.
(4) Carbon deposition in an amount of 2-5% based on the raw
material is unavoidable and, therefore, the yields of H.sub.2 and
CO are reduced. Further, a superfluous cost of equipment is
necessitated for the removal of carbon and recirculation into the
raw material. This is economically disadvantageous.
Various investigations have been made heretofore on the catalytic
gasification of heavy oils for the purpose of overcoming said
defects of the conventional processes for the partial oxidation of
heavy oils. Recently, several processes have been reported, though
they have not yet been put into practice on an industrial scale.
Those processes mainly comprise contacting a heavy oil with a
catalyst containing an alkali metal aluminate or calcium aluminate
which is a composite oxide of an alkali metal or alkaline earth
metal as the main component or a nickel catalyst containing a
tungsten compound to gasify the heavy oil by steam reforming or
partial oxidation.
Those processes have a merit that the gasification can be effected
at a temperature as low as 800.degree.-1300.degree. C. Therefore,
as compared with the non-catalytic partial oxidation process, those
processes have the merits of a higher gasification efficiency and a
smaller oxygen demand and, in addition, problems of materials of
the reactor are less serious. Another merit of those processes is
that the carbon deposition is small in amount and, therefore, the
apparatus and cost required for the recovery of the carbon deposit
are small.
However, after the gasification of the heavy oil in the presence of
those catalysts, lower hydrocarbons (particularly methane) remain
in a large amount in the resultant gas.
The presence of methane residue in the resultant gas is undesirable
when the gas is to be used as a raw material for the synthesis of
ammonia or methanol or as an oxo synthesis gas or as a source of
hydrogen for hydrogenation, though the methane residue is preferred
when the resultant gas is used as a fuel gas.
Thus, depending on the use of the resultant gas, the gas containing
a large amount of residual methane is undesirable. The separation
of methane residue from the resultant gas requires additional
apparatus and energy. This is disadvantageous from both economical
and industrial viewpoints.
It has been known that Fe, Co or Ni catalyst used in conventional
processes has a remarkable effect of reducing the methane content.
However, if this catalyst is used, carbon is easily deposited,
thereby deteriorating the catalytic capacity and in case of a fixed
bed system, the catalyst bed is sometimes clogged to make it
impossible to continue the operation. Though it is effective for
the prevention of carbon deposition to increase amount of steam,
additional energy is required therefor uneconomically.
It is considered that the methane content of the resultant gas can
be reduced by increasing the amount of steam, elevating the
reaction temperature or elongating the residence time in the
reactor. However, those ideas have a demerit of increasing the
energy requirement and the cost of apparatuses. Further, it is
difficult to reduce the methane content remarkably by those
ideas.
Under circumstances as set forth above, there has been eagerly
demanded the development of an economical process for obtaining a
gas rich in hydrogen and carbon monoxide by the continuous
catalytic gasification of heavy distillates such as kerosene, light
oil and No. 2 fuel oil and heavy residue at a temperature as low as
800.degree.-1300.degree. C. substantially without forming
hydrocarbon residue, particularly methane residue.
SUMMARY OF THE INVENTION
The object of the present invention is to obtain a gas rich in
hydrogen and carbon monoxide but having a very low methane content
by the continuous catalytic cracking of heavy distillates of a
specific gravity of higher than 0.7 such as kerosene, gas oil and
No. 2 fuel oil and heavy residues such as crude oil and atmospheric
residue at a temperature as low as 800.degree.-1300.degree. C.
The present invention relates to a process for the catalytic
gasification of heavy distillates of a specific gravity of higher
than 0.7, such as kerosene and gas oil, with steam and, if
necessary, an oxygen-containing gas, characterized in that the
heavy distillates are contacted with chromium oxide catalyst or a
catalyst comprising a mixture of chromium oxide and one or more of
alkaline earth metal oxides, aluminum oxide, zirconium oxide,
nickel oxide and cobalt oxide and that the heavy distillates are
contacted first with a gasification catalyst which depresses carbon
deposition such as calcium aluminate, an alkali aluminate or
tungsten-containing nickel catalyst prior to the contact thereof
with the chromium oxide catalyst or chromium oxide-containing
catalyst.
If a heavy distillate of a specific gravity of higher than 0.7 is
contacted with the catalyst mainly comprising chromium oxide
according to the process of the present invention, methane residue
in the resultant gas can be reduced and carbon deposition can be
inhibited.
If the heavy distillate is first contacted with a known
gasification catalyst comprising calcium aluminate, an alkali metal
aluminate or tungsten-containing nickel which depresses carbon
deposition (hereinafter referred to as a first catalyst bed) and
then contacted with a catalyst containing chromium oxide as
substantially the main component (hereinafter referred to as a
second catalyst bed or chromium catalyst), the prevention of carbon
deposition can be further completed, the amount of methane residue
can be reduced, the gasification temperature can be lowered and the
amount of steam to be added can be reduced.
Though the gasification of heavy residues of a specific gravity of
higher than 0.7 is difficult in general and carbon is apt to be
deposited, the gasification can be effected without causing the
carbon deposition on the catalyst bed and methane residue can be
reduced remarkably in amount by contacting the heavy residues with
the first catalyst bed containing calcium aluminate or the like and
then with the second catalyst bed.
The catalysts used for the gasification have excellent strength,
abrasion resistance, water resistance and gas resistance and they
satisfy requirements of industrially demanded physical properties.
A very important feature of the present invention is that the
gasification can be effected without causing the carbon deposition
on the catalyst bed or without poisoning with sulfur.
According to the present invention, the following significant
merits can be obtained:
(1) The resultant gas has a low residual methane content and the
yields of H.sub.2 and CO are high. Therefore, the gas is suitable
for the production of synthesis gas to be used for the synthesis of
ammonia and methanol.
(2) When the gas is used for the synthesis of ammonia and methanol,
the load due to the recycle of methane (inert component) in the
synthesis reactor is small, since the methane content of the gas is
extremely low. Accordingly, the power cost and capacity of the
devices can be reduced economically advantageously.
(3) The load for the separation of methane from H.sub.2 and CO can
be reduced to also reduce the cost of the apparatus and energy.
According to the process of the present invention, the defects of
conventional catalytic gasification processes are overcome as
described above and the essential merits of the catalytic
gasification processes superior to the non-catalytic processes can
be exhibited concretely. Namely, the process of the present
invention is superior to the conventional processes in the
following points:
(1) Gasification efficiency is higher and yields of H.sub.2 and CO
are higher, since the reaction temperature is lower by
200.degree.-600.degree. C.
(2) Amount of expensive oxygen required is smaller.
(3) Life of heat-resistant material of which the reactor is made is
longer and heat-resistant materials of a high quality are not
required.
(4) By the use of the catalyst, carbon deposition is reduced in
amount and, consequently, yields of H.sub.2 and CO are increased.
Therefore, the resultant gas is suitable for the preparation of
synthesis gas and a device for carbon recovery can be made smaller
economically advantageously.
DETAILED DESCRIPTION OF THE INVENTION
The term "heavy distillates" herein indicates distillation
fractions of a specific gravity of higher than 0.7 such as
kerosene, gas oil and No. 2 fuel oil. The term "heavy residue"
herein indicates hydrocarbon oils containing a residue remaining at
the bottom of a distillation column after an ordinary distillation
operation such as crude oil, atmospheric residue and vacuum residue
of a specific gravity of higher than 0.8. The term "heavy oil"
herein includes both heavy distillate and heavy residue.
Processes for the catalytic gasification of the heavy distillate or
heavy residue have yet not been put into practice on an industrial
scale. The present invention provides a novel industrial process
for the catalytic gasification of the heavy oils. More
particularly, the present invention provides a process for the
catalytic gasification of the respective heavy distillate and heavy
residue.
The process of the present invention for the catalytic gasification
of heavy distillate with steam or steam/oxygen-containing gas is
characterized in that the heavy distillate is contacted with
chromium oxide catalyst or a catalyst comprising a mixture of
chromium oxide and one or more of alkaline earth metal oxides,
aluminum oxide, zirconium oxide, nickel oxide and cobalt oxide.
The chromium oxide-containing catalysts (chromium catalysts) have a
chromium oxide content of 50-100 wt. %. The catalytic cracking
activity of the catalyst is mainly due to the chromium oxide.
Further, chromium oxide may be mixed with one or more of aluminum
oxide, zirconium oxide, alkaline earth metal oxides, nickel oxide
and cobalt oxide for the purpose of modifying the physical
properties such as the strength of the catalyst or inhibiting the
carbon deposition or as a promotor or filler. However, if the
chromium oxide content is less than 50 wt. %, the methane residue
is increased in amount and the economical advantage of the process
is reduced.
The chromium catalyst of the present invention has characteristic
features of inhibiting the carbon deposition and accelerating the
methane decomposition. For allowing the catalyst to exhibit those
characteristic features, the following conditions are required: The
heavy distillate is contacted with the catalyst at a temperature of
800.degree.-1300.degree. C. Namely, temperature at the exit of the
catalyst bed must be at least 800.degree. C. At a lower
temperature, the carbon deposition cannot be avoided, the operation
becomes unstable and methane residue is increased in amount
unfavorably. At a temperature above 1300.degree. C., energy
consumption for the gasification becomes excessive uneconomically.
Thus, the preferred temperature at the exit of the catalyst bed is
800.degree.-1300.degree. C.
The smaller is the amount of steam, the higher is the economy of
the process. However, if the amount of steam is insufficient,
carbon is easily deposited and methane residue is increased in
amount. Preferred S/C [steam (mole)/number of carbon atoms] in the
starting oil is 0.3-7.
Preferred residence time in the catalyst bed is 0.1-10 seconds. If
the residence time is less than 0.1 second, methane decomposition
is insufficient and carbon is apt to be deposited.
The methane decomposition becomes more complete as the pressure is
reduced. However, judging from the size of the equipment and total
economy of the process, pressures ranging from atmospheric pressure
to 100 atms. are preferred.
Another important requirement is to regulate the conditions prior
to the introduction into the catalyst bed. First, the heavy
distillate must be thoroughly mixed with a gasifying agent (steam
or steam/oxygen-containing gas). The heavy distillate may be
vaporized before it is mixed with the gasifying agent or,
alternatively, the liquid heavy distillate may be atomized with a
part or the whole of the gasifying agent for the mixing. In the
latter case, the velocity of the atomizing gas injected through a
nozzle is desirably higher than 100 m/sec. Temperature of the
thoroughly mixed heavy distillate and gasifying agent at an inlet
of the catalyst bed must be higher than 500.degree. C. At a lower
temperature, carbon deposition is caused easily on the catalyst
bed. For this reason, temperature of the mixture of the heavy
distillate and gasifying agent at the exit of the nozzle of the
reactor must be higher than 300.degree. C.
Another important condition is that the residence time of the
mixture of heavy distillate and gasifying agent fed through the
nozzle in a space before it reaches the catalyst bed is 0.05-5
seconds. If the residence time is shorter than 0.05 second, the
carbon deposition is caused in an upper part of the catalyst layer.
If the residence time is longer than 5 seconds, on the other hand,
carbon is deposited in said space and it might clog the catalyst
bed. The term "residence time" herein indicates a substantial time
of residence which is different from a value calculated by dividing
space volume by flow rate. Namely, it is undesirable that the space
before the inlet of the catalyst bed has a dead zone and a part of
the heavy distillate and the gasifying agent is resident therein
for longer than 5 seconds, even though the total average residence
time is within 5 seconds. It is important that the shape of the
space in the reactor is designed so that such a great distribution
of residence time is not caused. In case the shape cannot be
changed, it is required to introduce a gasifying agent such as
steam or air or the resultant gas through the dead space or to
circulate the resultant gas therein so as to eliminate the
excessive residence part.
The heavy distillate can be catalytically gasified by contacting
the heavy distillate and a gasifying agent with a chromium catalyst
under restricted conditions as described above. In addition, the
catalytic gasification can also be effected by the following
process.
The process comprises contacting the heavy distillate with a
gasification catalyst which depresses carbon deposition such as
calcium aluminate, an alkali aluminate or a tungsten-containing
nickel catalyst and then contacting the same with said chromium
catalyst.
This process is characterized in that the carbon deposition is
prevented as far as possible by contacting the heavy distillate
with a first catalyst bed which depresses carbon deposition and
that the operation flexibility is improved because of not requiring
the severe gasification conditions such as the space between the
nozzle and the catalyst bed, mixing condition in the catalyst bed,
temperature and residence time.
Further, economical merits of the process are expected in some
cases as described below.
For the completion of gasification, the residence times in the
first catalyst bed and the chromium catalyst bed must be prolonged
or the gasification temperature must be elevated, since
gasification activity is low and a considerable amount of methane
remains, even though the catalyst in the first catalyst bed has an
excellent effect of preventing carbon deposition. It might be
considered that the effect of economization is poor from only this
point of view. However, it is to be noted that as compared with the
gasification in the presence of only the chromium catalyst, the
amount of steam can be reduced and the gasification temperature can
be reduced, since the carbon deposition is inhibited even though
the residence time is prolonged under the same conditions. They are
factors for improving the economical merits of the process. Thus,
the process has both positive and negative economical factors and,
therefore, it cannot be evaluated indiscriminately. Either the
process for the gasification in the presence of only chromium
catalyst or the process for the gasification in the presence of the
combination of said catalyst with the first catalyst bed may be
selected in consideration of the use of resultant gas, the
conditions of location of the plant, the properties of the heavy
distillate, the costs of the starting oil and the utilities and
construction cost of the plant.
On the other hand, in the treatment of a heavy residue containing
distillation residue, the problem of carbon deposition is far more
serious. If the chromium catalyst is used alone, the carbon
deposition cannot be prevented even if gasification conditions such
as temperature, residence time, amount of steam and atomizing
method are altered considerably. For the prevention of carbon
deposition on the catalyst bed in the gasification of the heavy
residue, it is indispensable to contact the heavy residue with the
first catalyst bed prior to the contact thereof with the chromium
catalyst. By contacting the heavy residue then with the chromium
catalyst, methane the content of the resultant gas can be
reduced.
Now, description will be made on the process of the present
invention for the gasification of heavy distillates and heavy
residues wherein they are contacted with the first catalyst bed and
then the chromium catalyst.
The first and the second catalyst beds may be located close to each
other or, alternatively, they may be located separately from each
other to such an extent that no ill influence is given by the space
between them. The distance between them is such that the time
required of the mixture for moving from the first catalyst bed to
the second catalyst bed is preferably within several seconds. The
first and the second catalyst beds may comprise any combination of
fixed bed, fluidized bed and moving bed.
A gasifying agent such as steam, oxygen or oxygen-rich gas may
further be introduced between the first and the second catalyst
beds. In an embodiment, steam reforming is effected in the first
bed and partial oxidation is effected in the second bed.
The two-bed gasification process using said catalysts is
characterized in that higher hydrocarbons are converted into lower
hydrocarbons such as CH.sub.4, C.sub.2 H.sub.4 and C.sub.3 H.sub.6
in addition to H.sub.2, CO, CO.sub.2 and H.sub.2 O in the presence
of the first catalyst bed in the upper part of the reaction zone
and then the cracking and gasification of the hydrocarbons are
completed in the second catalyst bed in the lower part of the
reaction zone.
The two catalyst beds are used in the process of the present
invention. The first catalyst bed is filled with calcium aluminate,
an alkali aluminate or tungsten-containing nickel. The second
catalyst bed is filled with chromium oxide or a chromium
oxide-containing catalyst.
The calcium aluminate, alkali aluminate or tungsten-containing
nickel catalyst is a catalyst containing as the main component an
alkali aluminate or calcium aluminate which is a known alkali metal
or alkaline earth metal composite oxide or a tungsten compound
containing nickel catalyst.
A preferred filling rate in the first catalyst bed and the second
catalyst bed cannot be determined indiscriminately, since it varies
depending on the properties of the starting oil and the residence
time in the catalyst bed. The higher is the rate in the second
catalyst bed, the higher is the hydrocarbon-cracking activity and
the lower is the methane residue in the resultant gas.
In the gasification of a starting oil containing heavy residue such
as atmospheric residue or vacuum residue, if the amount of the
first catalyst bed is extremely small, the higher hydrocarbons are
contacted with the second catalyst bed before they have been
converted sufficiently into lower hydrocarbons such as CH.sub.4,
C.sub.2 H.sub.4 and C.sub.3 H.sub.6 and, consequently, carbon is
easily deposited on the second catalyst bed. If the filling rate in
the second catalyst bed exceeds 90 vol. % at a superficial velocity
in the column of 200 hr.sup.-1 based on the resultant gas of
atmospheric pressure, a very small amount of carbon deposit is
observed on the catalyst. If the filling rate is less than 25 vol.
%. the methane residue is increased in amount. Therefore, the
preferred filling rate in the second catalyst bed is 30-80 vol.
%.
In the gasification of distillates such as kerosene, gas oil and
U.S. No. 2 fuel oil, the filling rate in the second catalyst bed
can be increased, since the carbon deposition on the catalyst is
smaller than in case of heavy residue. Preferred filling rate is
generally higher than 50%, though it varies depending on
gasification conditions such as steam ratio and temperature. When
those oils are used, they can be gasified to yield carbon-free
gases which are suitable as ammonia, methanol or oxo synthesis gas
or as a starting gas of fuel cells.
Reaction conditions for carrying out the present invention are as
described below:
Preferred reaction temperature is 800.degree.-1300.degree. C.,
particularly 800.degree.-1100.degree. C. At a reaction temperature
of below 800.degree. C., carbon is easily deposited on the catalyst
bed sometimes to clog the catalyst bed and the continuous operation
becomes difficult. Preferred steam ratio [steam (mole)/carbon
(mole)] is above 0.3, particularly 0.3-7. If the steam ratio is
lower, carbon is deposited on the catalyst bed and, on the other
hand, a higher steam ratio is uneconomical. Preferred gasification
pressure ranges from atmospheric pressure to 100 Kg/cm.sup.2 and
preferred residence time in the reaction zone is 0.1-10
seconds.
The oxygen-containing gas used for the gasification by the partial
oxidation may be air, oxygen or a mixture of air and oxygen in any
desired ratio.
For further understanding of the present invention, examples of the
preparation of catalysts and reaction operations will be given,
which by no means limit the technical scope of the present
invention.
Preparation of catalyst of the first catalyst bed (catalyst A)
643 Parts of aluminous cement (comprising 80% of Al.sub.2 O.sub.3
and 19.5% of CaO) were mixed with 476 parts of calcium hydroxide.
The mixture was molded, calcined at 1300.degree. C. for two hours
and then pulverized. Thus resultant powder was kneaded with 5 wt. %
and 15 wt. %, based on the powder, of wheat flour and CMC solution
of 1.5% concentration, respectively. The mixture was molded into
tablets of a diameter of 10 mm and a height of 10 mm. The tablets
were calcined at 1330.degree. C. for 6 hours. Thus obtained calcium
aluminate catalyst had a compression strength of 350 Kg/cm.sup.2
and an excellent water resistance.
X-Ray diffraction of the catalyst revealed that the main component
was 12CaO.7Al.sub.2 O.sub.3 and a small amount of 3CaO.7Al.sub.2
O.sub.3 was recognized.
Preparation of catalysts of the first catalyst bed (catalysts B and
C)
One molecular amount of potassium carbonate was mixed with
6-molecular amount of aluminum hydroxide. The mixture was molded,
calcined at 1500.degree. C. for one hour and then pulverized. Thus
resultant powder was kneaded with 5 wt. % and 15 wt. %, based on
the powder, of sawdust and CMC solution of 1.5% concentration,
respectively. The mixture was molded into tablets of a diameter of
10 mm and a height of 10 mm. The tablets were calcined at
1500.degree. C. for 6 hours to obtain catalyst B. In the same
manner, catalyst C was prepared from sodium carbonate and aluminum
hydroxide. Those alkali aluminate catalysts had a compression
strength of higher than 300 Kg/cm.sup.2 and an excellent water
resistance.
X-Ray diffraction of the catalysts revealed that the main component
of them was RAl.sub.5 O.sub.8 and a small amount of R.sub.2
Al.sub.24 O.sub.37 was recognized (R being K or Na).
Preparation of catalyst of the second catalyst bed (catalyst D)
100 Parts of chromium oxide were kneaded together with 1.5 wt. %,
based on chromium oxide, of CMC solution of 1.8 wt. %
concentration. The mixture was molded into tablets of a diameter of
10 mm and a height of 10 mm. The tablets were calcined at
1300.degree. C. for 3 hours.
Thus obtained catalyst had an excellent water resistance and a
compression strength of 100-200 Kg/cm.sup.2. In handling the
catalyst, a slight pulverization was recognized but the catalyst
was still fit for use.
Preparation of catalyst of the second catalyst bed (catalyst E)
97 Parts of chromium oxide were thoroughly mixed with 3 parts of
magnesium oxide. 15 Weight %, based on the powder, of CMC solution
of 1.8% concentration was added thereto and the whole was kneaded
together and molded into tablets of a diameter of 10 mm and a
height of 10 mm. The tablets were calcined at 1300.degree. C. for 3
hours.
Thus obtained catalyst had an excellent water resistance and a
compression strength of 450 Kg/cm.sup.2. Degree of pulverization of
the catalyst in the handling was far reduced as compared with
catalyst D.
Preparation of catalysts of the second catalyst bed (catalysts F,
G, H, I, J, K and L)
The following catalysts were prepared in the same manner as in the
preparation of catalyst E:
______________________________________ Compression Water Catalyst
Components (wt. %) strength resistance
______________________________________ Catalyst F Cr.sub.2 O.sub.3
95% Al.sub.2 O.sub.3 5% 330 good Catalyst G Cr.sub.2 O.sub.3 50%
Al.sub.2 O.sub.3 50% 350 " Catalyst H Cr.sub.2 O.sub.3 25% Al.sub.2
O.sub.3 75% 300 " Catalyst I Cr.sub.2 O.sub.3 95% CaO 5% 220 "
Catalyst J Cr.sub.2 O.sub.3 97% ZrO.sub.2 3% 400 " Catalyst K
Cr.sub.2 O.sub.3 95% NiO 5% 320 " Catalyst L Cr.sub.2 O.sub.3 95%
CoO 5% 380 " ______________________________________
EXAMPLE 1
Kuwait atmospheric residue was partially oxidized with oxygen in
the presence of catalyst A or B alone or in the presence of both
catalysts A and E in various ratios in the first and the second
catalyst beds, respectively, in a reactor according to the present
invention. Results of the gasification are shown in Table 1.
It is apparent from Table 1 given below that methane residue in the
resultant gas can be reduced remarkably by filling catalysts A and
E in the two layers and that there exists a preferred range of
filling rates of catalysts A and E.
EXAMPLE 2
Kuwait atmospheric residue was partially oxidized with oxygen in
the presence of catalyst A filled in the first catalyst bed and one
of catalysts D, F, G, H, I, J, K and L in the second catalyst bed
in a reactor. Results are shown in Table 2. Carbon deposition on
the catalyst beds was not recognized in all cases.
EXAMPLE 3
Kuwait crude oil, atmospheric residue and vacuum residue were
subjected to continuous, catalytic gasification in the presence of
25 vol. % of catalyst A or B filled in the first catalyst bed and
75 vol. % of catalyst E filled in the second catalyst bed under
various reaction conditions. Results are shown in Table 3. In all
cases, methane residue in the resultant gas was very small and no
carbon deposition on the catalyst bed was recognized at all.
TABLE 1
__________________________________________________________________________
Run No. 1 2 3 4 5
__________________________________________________________________________
Catalyst first bed A B A A A 10 vol. % 25 vol. % 75 vol. % second
bed A B E E E 90 vol. % 75 vol. % 25 vol. % Reaction conditions
pressure (Kg/cm.sup.2) 1.0 1.0 1.0 1.0 1.0 Temp. (.degree.C.) (Note
1) 1000 1000 1000 1000 1000 steam ratio (mole/carbon mole) 1.5 1.5
1.5 1.5 1.5 ratio to theoretical oxygen (Note 2) 0.295 0.295 0.295
0.295 0.295 GHSV (hr.sup.-1) (Note 3) 200 200 200 200 200 Resultant
gas H.sub.2 50.4 51.6 57.3 57.3 57.1 CO 26.0 25.3 28.5 28.5 28.4
CO.sub.2 17.0 17.2 13.5 13.5 13.5 CH.sub.4 5.9 5.2 0.00 0.00 0.38
C.sub.2 H.sub.4 0.1 0.08 0 0 0 C.sub.2 H.sub.6 trace 0 0 0 0
H.sub.2 S 0.6 0.6 0.6 0.6 0.6 Carbon deposition on catalyst bed
none none trace of none none carbon deposit in the resultant gas
(wt. %) (Note 4) 0.40 0.52 0.30 0.28 0.30 Experiment time (hr) 5.0
5.0 5.0 5.0 5.0
__________________________________________________________________________
TABLE 2
__________________________________________________________________________
Run No. 6 7 8 9 10 11 12 13
__________________________________________________________________________
Catalyst first bed (25 vol. %) A A A A A A A A second bed (75 vol.
%) D F G H I J K L Reaction conditions pressure Kg/cm.sup.2 1.0 1.0
1.0 1.0 1.0 1.0 1.0 1.0 temp. .degree.C. 1000 1000 1000 1000 1000
1000 1000 1000 steam ratio (mole/carbon mole) ratio to theoretical
oxygen (-) 0.295 0.295 0.295 0.295 0.295 0.295 0.295 0.295 GHSV
(hr.sup.-1) 200 200 200 200 200 200 200 200 Resultant gas H.sub.2
57.1 53.1 56.1 55.9 56.0 57.2 56.5 56.2 CO 28.7 34.3 30.0 29.0 30.5
27.5 30.2 29.8 CO.sub.2 13.6 12.0 13.2 13.6 12.4 14.5 12.7 13.4
CH.sub.4 0.00 0.02 0.10 0.48 0.03 0.02 0.00 0.01 C.sub.2 H.sub.4
0.0 0.0 0.0 trace 0.0 0.0 0.0 0.0 H.sub.2 S 0.6 0.6 0.6 0.6 0.6 0.6
0.6 0.6 Carbon deposition on catalyst bed none none none none none
none none none in the resultant gas (wt. %) 0.36 0.56 0.37 0.43
0.38 0.52 0.38 0.33 Experiment time (hr) 5.0 5.0 5.0 5.0 5.0 5.0
5.0 5.0
__________________________________________________________________________
TABLE 3
__________________________________________________________________________
Run No. 14 15 16 17 18.sup.(Note 5)
__________________________________________________________________________
Catalyst first bed (25 vol. %) B A A A A second bed (75 vol. %) E E
E E E Starting oil crude Atmos- Atmos- Vacuum Vacuum oil pheric
pheric residue residue residue residue Reaction conditions pressure
(Kg/cm.sup.2) 6 1 9 50 1 temp. (.degree.C.) 950 1000 1000 1000 1000
steam ratio (mole/carbon mole) 3.8 3.8 1.0 1.5 1.5 ratio to
theoretical oxygen (-) 0 0 0.282 0.305 0.325 GHSV (hr.sup.-1) 900
300 1350 1350 200 Resultant gas H.sub.2 68.8 68.4 53.0 52.5 30.2 CO
17.0 17.9 34.1 34.5 14.6 CO.sub.2 12.0 12.9 12.1 11.4 9.6 N.sub.2 0
0 0 0 45.0 CH.sub.4 0.3 0.18 0.2 0.8 0 H.sub.2 S 0.3 0.42 0.6 0.9
0.6 Carbon deposition on catalyst bed none none none none none in
the resultant gas (wt. %) 0.05 0.10 0.6 1.0 0.8 Experiment time 24
240 30 30 720
__________________________________________________________________________
(Note 1) Temperature of the gas at the exit of the reactor.
(Note 2) Ratio to theoretical amount of oxygen required for the
complete combustion of the starting material.
(Note 3) Space velocity of the gas in the column in standard
state.
(Note 4) Wt. % based on the starting oil fed.
(Note 5) In the partial oxidation in Run No. 18, air was used as
the oxidized agent.
EXAMPLE 4
Catalyst A or B was filled in the first catalyst bed and catalyst E
or L was filled in the second catalyst bed in a reactor. Kerosene,
gas oil and No. 2 fuel oil were gasified under various reaction
conditions. Results are shown in Table 4. In all cases, methane
residue in the resultant gas was very small and no carbon
deposition on the catalyst bed or in the resultant gas was
recognized at all.
TABLE 4
__________________________________________________________________________
Run No. 19 20 21 22 23 24 25
__________________________________________________________________________
Catalyst first layer (vol. %) A B B A none none A (10%) (10%) (20%)
(20%) (10%) second layer (vol. %) E E L L E L E (90%) (90%) (80%)
(100%) (100%) (100%) (90%) Starting oil kero- gas kero- gas gas
kero- No. 2 Fuel sene oil sene oil oil sene oil Reaction conditions
pressure (Kg/cm.sup.2) 1 6 1 6 1 6 1 temp. (.degree.C.) 950 950
1000 1000 1000 1000 950 steam ratio (mole/mole) 1.0 1.0 1.0 3.8 1.0
3.8 1.0 ratio to theoretical oxygen (-) 0.2381 0.2414 0.2371 0
0.2589 0 0.2404 GHSV (hr.sup.-1) 400 1200 200 900 400 900 400
gasifying agent air air oxygen 0 air 0 air Resultant gas H.sub.2
38.6 37.3 59.3 70.1 36.4 70.3 37.6 CO 20.9 20.6 32.9 17.9 20.7 17.8
21.5 CO.sub.2 5.32 5.65 7.66 11.9 5.39 11.78 5.54 N.sub.2 35.1 35.9
0 0 37.5 0 35.3 CH.sub.4 0.05 0.52 0.05 0.09 0.01 0.09 0.04 H.sub.2
S -- 0.06 -- 0.08 0.06 -- 0.005 Carbon deposition on catalyst bed
none none none none none none none in the resultant gas none none
none none none none none Experiment time 5.0 30 24 5 20 20 5
__________________________________________________________________________
EXAMPLE 5
Catalyst E alone was filled in a reaction tube and light oil was
gasified. Residence time before reaching the inlet of the catalyst
bed (nozzle end) was varied. Results are shown in Table 5.
TABLE 5
__________________________________________________________________________
Run No. 26 27 28 29 30 31 32 33 34
__________________________________________________________________________
Catalyst first layer none none none none none none none none none
second layer E E E E E E E E E Starting oil gas gas gas gas gas gas
gas gas gas oil oil oil oil oil oil oil oil oil Pressure
Kg/cm.sup.2 6 6 6 1 1 1 1 1 1 Temp. (.degree.C.) 950 950 950 900
900 900 900 850 850 Steam ratio (mole/mole) 1.0 1.0 1.0 4.0 4.0 4.0
4.0 4.5 1.0 Ratio to theoretical 0.245 0.245 0.245 -- -- -- -- --
0.219 oxygen Catalyst bed GHSV (1/hr) 800 800 800 400 400 400 400
400 400 Residence time in a 0.02 0.1 6 0.02 0.1 2 6 0.1 0.1 space
on the catalyst (sec) Gasifying agent air air air steam steam steam
steam steam air Carbon deposition on catalyst Depo- None Depo-
Depo- None None Depo- None None sit sit sit sit in the resultant
gas Posi- Nega- Posi- Posi- Nega- Nega- Posi- Nega- Nega- tive tive
tive tive tive tive tive tive tive Experiment time 10 24 10 10 24
24 10 24 24 *1 *2
__________________________________________________________________________
Remarks *1 Steam is divided and supplied from the backside of the
nozzle. *2 A conical atomizing space is used.
* * * * *